REPLICAOF command in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Purpose of the REPLICAOF command

What is the primary purpose of the REPLICAOF command in Redis?

A To delete all keys in the current Redis database.

B To configure a Redis instance to replicate data from a specified master server.

C To create a backup snapshot of the current Redis database.

D To rename an existing key in the Redis database.

💡 Hint

Think about how Redis handles data replication between servers.

The REPLICAOF command tells a Redis server to become a replica of another Redis server, syncing data from the master.

❓ query_result

intermediate

Effect of REPLICAOF with no arguments

What is the result of running the command REPLICAOF NO ONE on a Redis replica?

A The Redis instance starts replicating from a random master.

B The Redis instance shuts down immediately.

C The Redis instance deletes all its data.

D The Redis instance stops replicating and becomes a master itself.

💡 Hint

Consider what happens when a replica stops following a master.

REPLICAOF NO ONE makes the Redis replica stop replicating and promotes it to a master role.

📝 Syntax

advanced

Correct syntax for making a Redis instance a replica

Which of the following commands correctly makes a Redis instance replicate from a master at IP 192.168.1.100 on port 6379?

A REPLICAOF 192.168.1.100 6379

B REPLICAOF 6379 192.168.1.100

C REPLICAOF MASTER 192.168.1.100 6379

D REPLICAOF TO 192.168.1.100:6379

💡 Hint

The command expects IP and port in order.

The correct syntax is REPLICAOF followed by the master's IP address and port number.

❓ optimization

advanced

Optimizing failover with REPLICAOF

In a Redis setup with one master and multiple replicas, which approach using REPLICAOF helps minimize downtime during master failure?

A Run REPLICAOF with the old master's IP on all replicas repeatedly.

B Restart all replicas to automatically detect the new master.

C Manually run REPLICAOF NO ONE on a replica to promote it, then update other replicas to replicate from the new master.

D Delete all replicas and create new ones after master failure.

💡 Hint

Think about how to quickly promote a replica and redirect others.

Manually promoting a replica with REPLICAOF NO ONE and updating others reduces downtime by quickly establishing a new master.

🔧 Debug

expert

Identifying error in REPLICAOF usage

Given the command REPLICAOF 192.168.1.50 executed on a Redis instance, what error will Redis return?

A ERR wrong number of arguments for 'REPLICAOF' command

B ERR invalid IP address format

C OK - replication started

D ERR unknown command

💡 Hint

Check how many arguments REPLICAOF expects.

REPLICAOF requires exactly two arguments: IP and port. Providing only one causes a wrong number of arguments error.